The walnut (Juglans regia L.) is in its own right an important component of anybody’s diet. It is often consumed without any further modification of let’s say the Mediterranean diet. Regular consumption of just 6 grams daily is claimed to provide many nutritional and health benefits (Tapia et al., 2013). Walnuts can also be pressed to produce a wonderfully nutty walnut oil which has its own health benefits. The oil is ideal on salads and is viewed as a rival to avocado oil in dietary terms.
The walnut kernel contains lots of oil which ranges between 52% and 70% w/w content. The oils are mainly polyunsaturated fatty acids (PUFAs) including linoleic acid (18:2) and linolenic acid (18:3) (Greve et al., 1992; Martínez et al., 2006).
The oil is produced by cold-pressing or through refining. Cold-pressed oil is more expensive because most of the beneficial compounds and nutrients are retained in the oil. Expression of the oil is similar to olive oil. Refined oil generally has a poorer nutrient profile so cold-pressed oils are always preferred for nutritional applications.
The oil fraction from the kernel almost has the perfect omega‐6/omega‐3 ratio which is close to 4∼6:1.
Shelf-Life Issues
The oil is sensitive, like many nut oils to oxidation because of its high polyunsaturated fatty acid content. The oil is always sold without the addition of antioxidants because it is a nutraceutical product (Martínez et al., 2011). This is always the case with other nut and most dietary oils because of the desire to claim purity in the product and avoid adulteration. Quality control for any oil is usually determined by establishing the degree of oxidation. This measure is a critical control parameter for walnut oil during processing and on storage. The two classic measures of peroxide value (PV) and p‐anisidine value (p‐AnV) have been established for walnut oil (Miraliakbari & Shahidi, 2008; Martínez et al., 2013; Vaidya & Eun, 2013a).
Benefits
The oil has a good omega-6 to omega 3 ration and is associated with reducing cardiovascular risk and heart attacks. There are no claims yet made for the oil although research continues to establish how beneficial the oil is (Martínez et al., 2010).
Treating Fungal Infections Of The Skin
Walnut oil is often found in skin lotions and oils for treating fungal infections of the skin. A whole host of infections including athlete’s foot, jock itch and Candida or Thrush are claimed to be treatable using the oil. The oil is often mixed with tea tree oil and garlic as a traditional remedy. Regular application is claimed to reduce reinfection and for the treatment of acne.
Treating Psoriasis
Psoriasis is an unpleasant skin condition similar to morphea where patchy itchy abnormal skin is generated. It is an autoimmune disease. The condition is triggered by infection, stress and cold weather. Dabbing walnut oil onto the effected area is claimed to reduce redness and inflammation.
Inflammatory Diseases
Nut oils including walnut oil have been consumed to ameliorate the conditions of eczema, arthritis and asthma.
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References
Greve, L. C., McGranahan, G., Hasey, J., Snyder, R., Kelly, K., Goldhamer, D., & Labavitch, J. M. (1992). Variation in polyunsaturated fatty acids composition of Persian walnut. Journal of the American Society for Horticultural Science, 117(3), pp. 518–522.
Martínez, M. L., Mattea, M. A., & Maestri, D. M. (2006). Varietal and crop year effects on lipid composition of walnut (Juglans regia) genotypes. Journal of the American Oil Chemists Society, 83(9), pp. 791–796. https://doi.org/10.1007/s11746-006-5016-z
Martínez, M., Barrionuevo, G., Nepote, V., Grosso, N., & Maestri, D. (2011). Sensory characterisation and oxidative stability of walnut oil. International Journal of Food Science & Technology, 46(6), pp. 1276–1281. https://doi.org/10.1111/j.1365-2621.2011.02618.x
Martínez, M. L., Labuckas, D. O., Lamarque, A. L., & Maestri, D. M. (2010). Walnut (Juglans regia L.): Genetic resources, chemistry, by‐products. Journal of the Science of Food and Agriculture, 90(12), pp. 1959–1967. https://doi.org/10.1002/jsfa.4059
Martínez, M. L., & Maestri, D. M. (2008). Oil chemical variation in walnut (Juglans regia L.) genotypes grown in Argentina. European Journal of Lipid Science and Technology, 110(12), pp. 1183–1189. https://doi.org/10.1002/ejlt.200800121
Martínez, M. L., Penci, M. C., Ixtaina, V., Ribotta, P. D., & Maestri, D. (2013). Effect of natural and synthetic antioxidants on the oxidative stability of walnut oil under different storage conditions. LWT‐Food Science and Technology, 51(1), pp. 44- 50. https://doi.org/10.1111/j.1750-3841.2008.00979.x
Miraliakbari, H., & Shahidi, F. (2008). Antioxidant activity of minor components of tree nut oils. Food Chemistry, 111(2), pp. 421–427. https://doi.org/10.1016/j.foodchem.2008.04.008
Tapia, M. I., García‐Parra, J., Ramírez, R., & Hernández, T. (2013). Comparative study of the nutritional and bioactive compounds content of four walnut (Juglans regia L.) cultivars. Journal of Food Composition & Analysis, 31(2), pp. 232–237 https://doi.org/10.1016/j.jfca.2013.06.004
Vaidya, B., & Eun, J. B. (2013a). Effect of temperature on oxidation kinetics of walnut and grape seed oil. Food Science and Biotechnology, 22(1), pp. 273–279. https://doi.org/10.1007/s10068-013-0077-x
Vaidya, B., & Eun, J. B. (2013b). Effect of roasting on oxidative and tocopherol stability of walnut oil during storage in the dark. European Journal of Lipid Science and Technology, 115(3), pp. 348–355. https://doi.org/10.1002/ejlt.201200288
Nice bit of writing. I love walnut oil in. My Chinese and Hong Kong recipes really benefit from this type of light oily flavouring.